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ilNITED STATES PATENT OFFICEC LUDWIG HERMANN PHILIPPI, OF HAMBURG, GERMANY.

METHOD OF PRODUCING PHOTO-RlLl EVOS.

SPECIFICATION forming part of Letters Patent No. 321,244, dated June 30, 1885.

Application filed January 8, 1883. (N0 specimens.) Patented in Italy October 4, 1882, No. 16/ 14636, and in Belgium October 16, 1882.

To all whom it may concern:

Be it known that I, LUDWIG HERMANN PHILIPPI, a subject of the Emperor of Germany, and a resident of Hamburg, in the German Empire, have invented certain new and useful Improvements in Producing Photo-Rilievos with equally deepened excavations, of which the following is a specification.

My invention relates to. improvements in photo-rilievos which are produced by etching; and the object of my improvements is to etch the figures of such rilievos to a uniform and equal depth. To attain this object I cover a plate, made of any suitable material that will not be affected or corroded by the etching-acid, with a layer of the material to be etched, such layer being spread equally over the plate and of a uniform thickness. Then I cover the layer with a protecting-couch of etching-varnish, gelat-ine, printing-ink, &c., which is afterward removed at all the places where the layer is to be etched, or a photographic picture or design may be formed upon the surface of the plate in the usual manner of forming photo-engravings. WVhen a plate thus prepared is exposed to the etchingacid, the upper layer will be eaten away at all the points that are not covered by the protecting-couch; but the excavations thus produced cannot go farther down or penetrate farther than the non-corrosive base.

Having thus fully described my invention, I

claim and desire to secure by Letters Patent 1. The process of producing photo-rilievo engravings having depressions of equal depth upon their surface, which consists of covering a plate of non-corrosible material with a uniform layer of corrosible material, forming the design upon the said corrosible material in non-corrosible varnish, and etching away the exposed portions of the corrosible material down to the non-corrosible plate, substantially as set forth. V

2. Aphotorilievo engraving as produced by the hereinbefore described process, consisting of a uniform layer of corrosible material in combination with a non-corrosible base-plate, so that the depressions etched through the said corrosible material are of equal depth all over the plate, substantially as set forth.

In testimony that I claim the foregoing as my inventionIhave signed my name, in presence of two witnesses,this 11th day of December, 1882.

LUDWIG HERM ANN PHILIPPI. Witnesses:

ALEXANDER Srnonr, EMIL HAASE. 

